In the course of processing a photographic element containing an imagewise exposed silver halide emulsion layer reduced silver can be formed either as a direct or inverse function of exposure. At the same time, at least a low level of reduced silver formation also occurs independently of imagewise exposure. The term "fog" is herein employed to indicate the density of the processed photographic element attributable to the latter, usually measured in minimum density areas. In color photography fog is typically observed as image dye density rather than directly as silver density.
Over the years a variety of differing materials have been introduced into silver halide emulsions to inhibit the formation of fog. Research Disclosure, Vol. 176, December 1978, Item 17643, Section VI, lists the more commonly employed fog inhibiting agents. Research Disclosure is published by Kenneth Mason Publications, Ltd., The Old Harbourmaster's, 8 North Street, Emsworth, Hampshire PO10 7DD, England.
It is known to employ as fog inhibiting agents compounds having two aromatic nuclei linked by two divalent sulfur atoms and analogous compounds in which one or both of the sulfur atoms are replaced by selenium atoms. Exemplary of such fog inhibiting agents are bis(p-aminophenyl)disulfides disclosed by Millikan et al U.S. Pat. No. 3,397,986.
Asahi Japanese Kokai No. 57817/78, laid open May 25, 1978, discloses the use of a variety of tellurium compounds as chemical sensitizers for silver halide emulsions. In one of a variety of differing forms the tellurium compounds can satisfy the formula EQU R.sub.1 --Te--Te--R.sub.2
wherein R.sub.1 and R.sub.2 are organic groups, such as substituted or unsubstituted alkyl or aryl groups or carbonyl containing organic groups. Aryl substituents disclosed are methyl, ethyl, methoxy, amino, dimethylamino, hydroxy, and halogen.
Lok et al U.S. Ser. No. 719,839, filed Apr. 4, 1985 concurrently herewith, titled DIVALENT CHALCOGENIDE FOG INHIBITING AGENTS FOR SILVER HALIDE PHOTOGRAPHY, commonly assigned, discloses aromatic tellurochalcogenides to be useful silver halide fog inhibiting agents.
Ludwig Reichel and Ernst Kirschbaum, Uber Aromatsiche Tellurverbindungen (I. Mitteilung uber Organometallverbindungen), Analen der Chemie, Vol. 523, 1936, pp. 211-221, describes the preparation of bis(4-acetamidophenyl)ditelluride.
Cobbledick et al, "Some New Organotellurium Compounds Derived from Azobenzene: The Crystal and Molecular Structure of (2-Phenylazophenyl-C,N')tellurium(II) Chloride", Journal of Chemical Research, pp. 1901-1924, 1979, discloses 2,2'-ditellurobisbenzenamine.